Db Measurements - HP E1312A User Manual

Two Ways to Store the
NULL Offset Value

dB Measurements

42 HP E1312A/E1412A Multimeter Application Information
•
The null value is stored in the multimeter's Null Register. You can
enter a specific number into the null register using the
CALCulate:NULL:OFFSet <
value is replaced with the new value. Use the following commands to
activate the NULL function and input a null value. The calculate state
must be enabled before you can store a value in the Null Register.
function
CONF:<
CALCulate:FUNCtion NULL
CALCulate:STATe ON
CALCulate:NULL:OFFSet <
•
Another way to enter the null value is to let the multimeter store the
first reading in the register. After you enable the
the CALC:STATe ON
be zero (if you have not stored a value as described in the previous
bullet). The measured value is stored as the
subtracted from itself to result in the zero reading. All subsequent
measurements will have the offset value subtracted from them. If you
previously stored a
CALC:NULL:OFFS <
the first reading does not overwrite the stored offset value but returns
with the previous offset value subtracted.
CONF:< function
CALCulate:FUNCtion NULL
CALCulate:STATe ON
** Set up the system to generate the offset of concern (e.g., short
** input leads for 2-wire ohms measurements that will follow).
READ?
Each dB measurement is the difference between the input signal and a stored
relative value, with both values converted to dBm.
dB = reading in dBm - relative value in dBm
•
Applies to dc voltage and ac voltage measurements only.
•
The relative value is adjustable and you can set it to any value between
0dBm and ±200.00dBm (well beyond the multimeter's measurement
capabilities).
•
Clearing the relative value. The relative value is stored in volatile
memory; the value is cleared when power is removed, after the module
is reset or after a function change.
value command. Any previously stored
>
Clears the null offset value.
>
Set math function to NULL.
Enable math operation.
value Store a null offset value.
>
command, the first measurement you obtain will
offset value using
NULL
value as in the commands in the above bullet,
>
> Clears the null offset value.
Set math function to NULL.
Enable math operation.
Measures and stores the offset value.
function with
NULL
offset value and
NULL
Chapter 2